The present invention relates to a tube which is charged with explosives and a method of blasting bedrock using the same, and more particularly, to an explosive tube, which is charged with explosives and is inserted into a hole bored in a bedrock, and a method of blasting a bedrock using the same.
In general, blasting construction means construction for blasting bedrocks, such as cutting work of raw stones in a mine or a quarry, tunneling work in a rock field, cutting work of a concrete structure and road opening work, and recently, blasting construction, such as underground excavation work, power cable work and pipe construction for a building, and subway construction, has been frequently carried out in downtown areas.
The blasting construction includes not only work to crunch big stones into little pieces but also a larger work to explode several tons of stones at the same time, and has been carried out through designs using construction methods defined by each pattern.
Conventional bedrock blasting methods which have been widely used are divided into a general blasting method of drilling a blast hole in a bedrock, charging the inside of the blast hole with explosives and tamping materials and carrying out explosion, a blasting method by deck charge of arranging explosives and tamping materials by turns inside a hole and carrying out explosion in order to reduce vibration, and a pre-split blasting method carried out to arrange the slope.
Moreover, for blasting, ammonium nitrate fuel oil (ANFO) explosives, bulk explosives, water gel explosives and so on have been used. The ANFO explosives have been the most generally used due to economic feasibility because being ammonium explosives in which ammonium nitrate is mixed with fuel oil, but need primers or boosters, are difficult to be stored for a long time because of absorptiveness and weak in water resistance.
FIG. 1a is a sectional view of a general blasting method by conventional explosives. In FIG. 1a, initial explosives 2, detonators 3 and explosives 4, such as ANFO explosives or bulk explosives, are loaded inside a charge hole 1 of a bedrock, the remaining space is tamped with tamping materials 5, and then, explosion is carried out. However, such a general blasting method has several disadvantages in that it generates big vibration and explosive sound and there is a risk of shattering because the initial explosives 2 loaded inside the charge hole 1 are blasted in concentration on the lower part of the charge hole 1, in that there is high probability of generating boulder stones, which are bulk rocks, because the tamping materials 5 are relatively longer than the depth of the bored hole and explosive power cannot reach the bedrock around the tamping materials, in that it is uneconomical because excessive explosives are used due to over-charging, in that a detonator lead gets longer due to indirect priming, and in that ANFO explosives may cause static electricity.
In order to overcome the above disadvantages, FIG. 1b is a sectional view showing the blasting method by deck charge by conventional explosives. As shown in FIG. 1b, according to the blasting method by deck charge, the step of loading initial explosives 2, detonators 3 and explosives 4, such as ANFO explosives or bulk explosives, inside a charge hole 1 and the step of tamping the tamping materials 5 are carried out by turns to form a stratiform charge, and in this instance, the detonators 3 are individually loaded as many as the number of the stratiform charges so that the explosives are individually exploded inside the same hole at specified time intervals to crush rocks. However, the blasting method by deck charge has several disadvantages in that it is expensive and complicated because it requires the detonators as many as the number of the stratiform charges, in that it is inefficient and uneconomical because it is difficult to load the explosives 4 and the tamping materials 5 by turns, and in that damping effect of vibration or explosive sound is not good because explosives of the same amount must be used.
Moreover, Korean Patent No. 10-0882851 published on Feb. 10, 2009 discloses a method for blasting rocks using an air deck filled with rocks, which forms an air deck space between an explosive and an explosive or between an explosive and a tamping material inside a charge hole. However, the blasting method is a method of directly charging explosives and tamping materials inside the charge hole, in case of ANFO explosives which have weak water resistance, the method cannot be easily applied to geographical features of Korea which have lots of underground water and cavities, and it is difficult to realize quantification of explosives.
Furthermore, in general, in order to crush rocks, explosives are excessively concentrated on the lower part. Additionally, the existing cushion blasting method is a method of blasting by binding explosives to detonating fuses at regular intervals, but is not used widely because it is complicated and uneconomical due to a high price of the detonating fuses.